Musical tone wave shape generating apparatus

ABSTRACT

A plurality of memories are provided for storing, in analog representation, the sampled valves of a one cycle sinusoidal wave of the fundamental frequency, a two cycle sinusoidal wave of the second harmonic, . . . and an m cycle sinusoidal wave of the m-th harmonic. These memories are read at the same reading rate. The read out sinusoidal wave are controlled in their relative levels in accordance with the tone-color and amplitude of a musical tone wave shape to be obtained. The sinusoidal waves thereafter are synthesized to produce the desire tone-color wave shape. The levels of the read out sinusoidal waves are controlled by changing the amplification degree of variable amplifiers respectively provided on the output side of the respective memories. Alternatively, memories are provided for storing these sinusoidal waves digitally. The digital signals read from these memories are applied to corresponding multipliers. The multipliers receive, on the other hand, digital control signals for controlling the level of each sinusoidal wave in accordance with the tone-color and amplitude of the musical tone wave shape to be obtained. These two kinds of digital signals are multiplied with each other in these multipliers. The outputs of the multipliers are applied to an adder, where they are added together. A digital signal representing the addition result is converted to an analog signal by a digital-to-analog converter to produce the desired musical tone wave shape.

United States Patent [191 Tomisawa et a1.

[ June 28, 1974 MUSICAL TONE WAVE SHAPE GENERATING APPARATUS [73] Assignee: Nippon Gakki Seizo Kabushiki Kaisha, Shijuoka-ken, Japan 22 Filed: Jan. 15, 1973 1211 Appl. No.: 323,582

[30] Foreign Application Priority Data Jan. 17, 1972 Japan 47-6754 Jan. 17, 1972 Japan.,.. 47-6755 Jan. 17, 1972 Japan 47-6756 [52] US. Cl 340/172.5,84/1.01, 84/127 [51 Int. Cl. Gloh 1/00, G061 7/00, (1061' 13/00 [58] Field of Search 340/1725; 84/1.0l, 1.02, 84/103, 1.28, 345, D16. 29, 1.27

[56] References Cited UNITED STATES PATENTS 2,530,251 11/1950 Luberoff 84/170 2.940.351 6/1960 Chamberlin 84/128 3,515,792 6/1970 Deutsch"... 84/103 3,610,799 10/1971 Watson 84/101 3,610,801 10/1971 Fredkin..... 84/103 3,639,913 2/1972 Watson 340/1725 3,647,661 10/1972 Deutsch 84/].01 3,647,929 3/1972 Milde, Jr 84/101 3,659,488 5/1972 Deutsch 84/345 3,696,201 10/1972 Arsem 84/l.0l 3,699,492 10/1972 Yoshihara 338/69 3,733,593 5/1973 Molnar 340/1725 IBM Techinical Disclosure Bulletin, Vol. 15, No. 3,

August 1972,

Primary Examiner-Paul .l. Henon Assistant ExaminerJames D. Thomas Attorney, Agent, or Firm-Ladas, Parry, Von Gehr, Goldsmith & Deschamps 57] ABSTRACT A plurality of memories are provided for storing, in analog representation, the sampled valves of a one cycle sinusoidal wave of the fundamental frequency, a two cycle sinusoidal wave of the second harmonic, and an m cycle sinusoidal wave of the m-th harmonic. These memories are read at the same reading rate. The read out sinusoidal wave are controlled in their relative levels in accordance with the tone-color and amplitude of a musical tone wave shape to be obtained. The sinusoidal waves thereafter are synthesized to produce the desire tone-color wave shape. The levels of the read out sinusoidal waves are controlled by changing the ampliflcation degreeof variable amplifiers respectively provided on the output side of the respective memories.

Alternatively, memories are provided for storing these sinusoidal waves digitally. The digital signals read from these memories are applied to corresponding multipliers. The multipliers receive, on the other hand, digital control signals for controlling the level of each sinusoidal wave in accordance with the tone-color and amplitude of the musical tone wave shape to be obtained. These two kinds of digital signals are multiplied with each other in these multipliers, The outputs of the multipliers are applied to an adder, where they are added together. A digital signal representing the addition result is converted to an analog signal by a digital-to-analog converter to produce the desired musical tone wave shape.

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SHEET 3 BF 4 ADD ML3 DA M I 8bits 1 arms ts i 3 i E E 4, 2 5 8mm" 5 V Ram VR VR i w I x 0 b h x MUSICAL TONE WAVE SHAPE GENERATING APPARATUS This invention relates to a musical tone wave shape generating apparatus and, more particularly, to a musical tone wave shape generating apparatus capable of producing a musical tone wave shape of a desired tonecolor by synthesizing a fundamental wave and a plurality of harmonics which are in harmonic relation with the fundamental frequency at appropriate ratio according to the desired tone-color.

A musical tone wave shape can be divided into a fundamental wave component and one or more harmonic components, no matter how complicated the wave shape may appear. Conversely, a desired musical tone wave shape can be obtained by synthesizing its fundamental wave and one or more predetermined harmonics at appropriate ratios of levels. The present invention makes use of this principle.

A specific musical tone wave shape may be obtained by providing a memory which stores this specific musical tone wave shape and reading it from the memory. It is very difficult, however, to change the contents once stored in the memory. In order to obtain a plurality of differe nt musical tone wave shapes, it is therefore necessary to provide a plurality of memories which respectively store one of the different wave shapes. If the number of required musical tone wave shapes is large, a corresponding large number of memories are required. Furthermore, a desired musical tone wave shape will not always be obtained from one of these memories if the desired wave shape is not stored in any of the memories.

It is, therefore, an object of this invention to provide an apparatus capable of producing any desired musical tone wave shape by using only a small number of memories.

It is another object of the invention to provide an apparatus capable of producing a desired musical tone wave shape by providing a plurality of memories which respectively store, in sampled analog representation, the fundamental frequency of the musical tone wave shape and a plurality of its harmonics and reading these waves simultaneously from these memories and synthesizing the read out outputs at a suitable relative level ratio.

It is another object of the invention to provide an apparatus capable of producing a desired musical tone wave shape by providing a plurality of memories which respectively store, in digital representation, the fundamental wave and a plurality of its harmonics, reading information corresponding to these waves simultaneously from these memories, multiplying digitally the relative levels of the read out outputs with each other, thereafter adding digitally the read out outputs to gether and converting the digital signal to an analog signal to produce the desired musical tone wave shape.

It is another object of the invention to provide an apparatus in which the relative levels of the outputs read from a plurality of memories respectively storing digitally the fundamental wave and its harmonics are controlled in accordance with the outputs of spectra memories which store digitally predetermined relative levels of these outputs.

These and other objects and features of the invention will become apparent from the description made hereinbelow with reference to the accompanying drawings in which:

FIG. 1 is a block diagram showing one embodiment of the musical tone wave shape generating apparatus according to the invention;

FIG. 2 is a circuit diagram showing one example of the wave shape memory shown in FIG. 1;

FIG. 3 is a block diagram showing another embodiment of our musical tone wave shape generating apparatus incorporating memories which store wave shapes in digital representation;

FIG. 4 is a block diagram showing another embodiment of our musical tone wave shape generating apparatus incorporating memories which, like the ones shown in H6. 3, store wave shapes in digital representation and further incorporating spectra memories which store digitally predetermined relative levels of the fundamental wave component and each harmonic component of a desired musical tone wave shape.

Referring first to FIG. 1, a clock pulse generator 1 provides, according to the note to be played, pulses of NfHz to a counter 2 of n (e.g. 6) stages (where N 2 and f represents the fundamental frequency of the musical tone wave shape to be obtained). Wave shape memories M, through M respectively store sinusoidal waves. The memory M, stores the fundamental wave, M the second harmonic M the m-th harmonic. In the preparation of each memory, each wave shape to be stored is sampled by a suitable sampling number N (e.g. 64) and the wave shape amplitudes at respective sample points are stored in analog values. The fundamental wave memory M, stores amplitudes of one cycle of a sinusoidal wave, the second harmonic memory M stores amplitudes of two cycles of a sinusoidal wave and each subsequent memory stores in the same manner amplitudes of cycles of a sinusoidal wave to be stored. The bit output of each stage of the counter 2 is provided to decoders D, through D,, simultaneously. Each of the decoders D, through D,,, provides, upon receipt of each bit output of the counter 2, its output on one of its individual output lines L, through L one after another according to the state of the bit output, just as the outputs from a ring counter. Accordingly, when a pulse is applied from the clock pulse generator 1 to the counter 2 in a reset state, the decoders D, through D,, produce outputs on the output lines L,. When a next pulse is applied to the counter 2, the decoders D, through D,,, produce outputs on the output lines L Thereafter the decoders D, through D,, produce outputs on the output lines L,. L, one line after another, each time a clock pulse is applied to the counter 2. After the output line L,,, the output is again produced on the output line L, and this process is repeated cyclically.

FIG. 2 shows one example of construction of the memories M, through M,,,. A sinusoidal wave to be stored is sampled by the sampling number N and the amplitude at each sample point is stored by means of resistor values according to a predetermined voltage dividing ratio. Reference character A, designates a connection point of resistors R, and R, A, a connection point of resistors R and R and A a connection point of resistors R and R respectively. Since a constant voltage is applied between a terminal T,, and ground, voltages at these connection points A, through A" are Rmv/Ru, Rm, R ,,V/R Ru, R V/R R respectively. These voltages respectively correspond to the values of amplitudes of the wave shape to be stored. The drains of transistors T, through T are respectively connected to the corresponding connection points A, through A,,. The source of each of the transistors T, through T,, is connected to the sources of 5 its adjacent transistors in common and also to an output terminal Tout. The gates of these transistors T, through T,, are respectively connected to the output lines L, through L,,.

Accordingly, when the decoder D produces outputs successively on the output lines L,, L L,,, the transistors T, through T conduct in time sequence and provide the above described predetermined voltages to the output terminal Tout. Thus the sinusoidal wave shape stored in the memory M is read out.

Referring again to FIG. 1, variable amplifiers VA, through VA are respectively connected to the output terminals of the memories M, through M to control the levels of the wave shape outputs of the memories M, through M,,,. The wave shape outputs thus controlled in their level by the variable amplifiers VA, through VA are thereafter synthesized and taken out of an output terminal 3.

The amplificiation factors of the variable amplifiers VA, through VA are variable in accordance with the values of voltages applied thereto (hereinafter called control signals). These control signals are produced in gain control circuits C, through C,,,, which will be described more in detail hereinbelow.

Tone-color selection and control knobs Sa through Sh are provided corresponding to tone-colors A through H to be obtained. The sliders of variable resistors VRa through VRh are operable by manipulation of these knobs Sa through Sh. A constant voltage V is applied to one end of each of these variable resistors VRa through VRh. The slider of the variable resistor VRa is connected to the input terminals of the gain control circuits C, through C,,, via resistors Ra,, Ra, Ram. Similarly, the slider of the variable resistor VRb is connected to the input terminal of the gain control circuits C, through Cm via resistors Rb,, Rb Rbm. The sliders of the other variable resistors are likewise connected to the input terminals of the gain control circuits C, through C,,,.

The resistors Ra, through Ram are provided to determine the ratio of levels of the fundamental wave, the second harmonic, and the m-th harmonic whereas the variable resistor VRa is provided to obtain the tonecolor wave shape thus constituted at a desired level or amplitude. The foregoing description is also applicable to the other resistors Rb, through Rbm, Rh, through Rhm and the variable resistors VRb through VRh.

For convenience of explanation, let it be assumed that the knobs Sb through Sh and a knob Sx to be described later are set at a 0 amplitude position and the knob Sa is set at a suitable position other than 0 amplitude. The gain control circuit C, receives a voltage which is determined by the resistor Ra, and the position of the slider of the variable resistor VRa. This d-c voltage is amplified in the gain control circuit C, and thereafter is applied to the control terminal of the variable amplifier VA, as the control signal. Accordingly, the amplification factor of the variable amplifier VA, becomes one which corresponds to the control signal and the fundamental wave output of the memory M, is taken out of the output terminal of the variable amplifier VA, at a level which corresponds to this amplification factor. The gain control circuit C, likewise receives a voltage which is determined by the resistor Ra, and the position of the slider of the variable resistor VRa and controls the level of the second harmonic output. The same is the case with the other harmonic outputs.

Thus, a predetermined musical tone wave shape at a predetermined level is produced by setting the tonecolor selection and control knob at a suitable position. Other predetermined musical tone wave shapes at predetermined levels are also produced by manipulating the knobs Sb Sh.

lf several knobs are selected and set at suitable positions, a composite voltage of the set levels of the tonecolors corresponding to these selected knobs is provided at the output terminal of each of the control circuits C, through C,, as the control signal for each of the fundamental wave, the second harmnic the m-th harmonic. Consequently, a musical tone wave shape which is composed of said plurality of tone-colors is provided at the output terminal 3 at a desired level.

FIG. 3 shows another embodiment of the musical tone wave shape generating apparatus according to the invention. The main difference between the present embodiment and the above described embodiment is that wave shape memories Ma, through Mam used in the present embodiment store the wave shape amplitudes digitally and that the wave shapes which are simultaneously read from these memories are digitally controlled in their levels and synthesized and thereafter are converted to analog signals to produce the desired musical tone wave shape. Hence the same component parts in FIGS. 1 and 3 are designated by the same reference characters and a detailed explanation of these component parts will be omitted in the description to follow.

Each of the wave shape memories Ma, through Mam consists, for example, of a read only memory (ROM) which stores amplitudes at respective sample points of the sampled sinusoidal wave in the form of binary information consisting of multiple bits. The memory Ma, stores the fundamental wave, Ma the second harmonic and Mam the m-th harmonic respectively. The fundamental wave memory Ma, stores amplitudes of one cycle of a sinusoidal wave, the second harmonic memory Ma stores amplitudes of two cycles of a sinusoidal wave and each subsequent memory stores in the same manner amplitudes of m cycles of a sinusoidal wave. Each wave shape to be stored in these memories is sampled by a sampling number N (e.g. 64).

As the outputs of decoders D, through Dm are successively applied to the memories Ma, through Mam, digital signals representing the stored amplitudes are successively read from these wave shape memories Ma, through Mam. These digital signals consist, for example, of eight bits. Multipliers ML, through MLm are respectively connected to the memories Ma, through Mam. The multipliers ML, through MLm multiply the digital signals thus read from the memories Ma, through Mam with control signals to be described later, thereby controlling the levels of the outputs of the memories Ma, through Mam in response to the control signals. The controlled outputs are taken out as digital signals consisting, for example, of eight bits. The control signals are also digital signals consisting, for example, of five bits.

Assume now, for convenience of explanation, that tone-color selection and control knobs Sb through Sh and Sx are set at a amplitude position and a tonecolor selection and control knob Sa is set at a suitable position other than the 0 amplitude position. A voltage determined by a resistor Ru, and the position of the slider of a variable resistor VRa is applied to the input terminal of an analog-to-digital converter A,. This voltage is converted by the analog-to-digital converter A, to a binary signal of a suitable number of bits, e.g. and applied to the multiplier ML, as a control signal. Accordingly, the digital signal from the memory M, is multiplied with this control signal in the multiplier ML,, and the result (mathematical product) of the multiplication is provided as the output of the multiplier ML,. This output contains, for example, eight digits counting from the most significant digit, the remaining digits being discarded. The contents of the eight bit digital signal produced at the output terminal of the multiplier ML, represent a wave shape amplitude of the fundamental wave controlled in its level by the above described control signal. In other words, the fundamental wave output controlled in its level is provided in the form of a digital signal at the output of the multiplier ML,. Similarly, a voltage determined by a resistor Ra, and the position of the slider of a variable resistor VRb is applied to an analog-to-digital converter A The analog-to-digital converter A, converts this voltage to a digital signal and applies it to the multiplier ML, as a control signal, thereby causing the multiplier ML, to produce the second harmonic output controlled in its level in the form of a digital signal. The same principle of operation applies to the other harmonic outputs from the multipliers ML, through MLm.

Digital signals produced in the multipliers ML, through MLm are applied to an adder ADD where these signals are added together. The result of the addition is provided as the output of the adder ADD in the form of a digital signal containing, for example, twelve digits counting from the most significant (i.e., highest order) digit. This digital signal is applied to a digital-toanalog converter DA where it is converted to an analog signal and taken out of an output terminal 3. it will be understood from the foregoing description taht this output is a synthesized musical tone wave shape composed of the sinusoidal wave outputs from the memories Ma, through Mam which are controlled in their levels by the control signals from the analog-to-digital converters A, through Am.

Thus, a predetermined musical tone wave shape at a predetermined level is obtained by setting the tonecolor selection and control knob Sa at a suitable position. Other predetermined musical tone wave shapes at desired levels are also obtainable by manipulating the other knobs Sb through Sh.

If several knobs are set at suitable positions, a composite voltage of the levels of the selected tone-colors is applied to each of the an alog-to-digital converters A, through Am for controlling the fundamental wave and each harmonic. Accordingly, a musical tone wave shape composed of said plurality of tone-colors is provided at the output terminal 3.

in the foregoing two embodiments, the resistors Ra, through Ram, Rb, through Rbm, Rh, through Rm respectively have predetermined values of resistance for determining the relative levels of the fundamental wave and each harmonic. and predetermined musical tone wave shapes are obtained by manipulating the knobs 50 through Sh. For obtaining a special tone-color other than these predetermined tone-colors, variable resistors Rx, through Rxm may be inserted in addition to the fixed resistors between the knob Sx and the gain control circuits C, through Cm in the case of the embodiment shown in FIG. 1, and between the knob Sr and the analog-to-digital converters A, through Am in the case of the embodiment shown in FIG. 3. The resistance of these variable resistors Rx, through Rxm can be individually adjusted to suitable values. Reference characters VRx designate a varaible resistor which can be operated by the knob Sx.

[n the embodiments described above, the variable resistors VRa through VRx may be replaced by tapped resistors and change over switches. In this case, a synthesized musical tone wave shape determined by the relative state of these switches is provided at the output terminal 3, although the apparatus is incapable of variably controlling the amplitude of each tone-color continuously.

FIG. 4 shows another embodiment of the apparatus according to the invention. This embodiment is different from the embodiment shown in FIG. 3 in the circuit arrangement for producing control signals applied to the multipliers ML, through MLm. In FIGS. 3 and 4, the same component parts are designated by the same reference characters and a detailed explanation of these component parts will be omitted in the description to follow.

in FIG. 4, switch knobs S, through 8,, are provided as tone-color selection knobs. The tone-color selection knobs S, through S respectively correspond to tonecolors to be obtained and are adapted to operate the sliders of variable resistors VR, through VR A constant voltage is applied to one end of each of the variable resistors VR, through VR The sliders of the variable resistors VR, through VR,, are respectively connected to analog-to-digital converters Aa, 11 The voltage applied to the analog-to-digital converters An, through Aago is converted to digital signals X, through X consisting, for example, of four bits. These digital signals X, through X are applied to the input terminals on one side of multipliers MM, through MM These signals X, through X respectively represent each tone-color and its amplitude.

Each of spectra memories SM, through 8M consist, for example, of a read only memory (ROM) and stores digitally a signal for determining the relative levels of the fundamental wave and each harmonic of the desired musical tone wave shape.

Assume, for convenience of explanation, that the knob S, is set at a suitable position other than a 0 amplitude position, that the analog-to-digital converter Aa, produces the output X, and that the remaining knobs 8, through S are all set at the 0 amplitude position. The spectra memory SM, provides a digital signal K, consisting, for example, of five bits and determining the level of the fundamental wave, a digital signal K, determining the level of the second harmonic and a digital signal Km determining the level of the m-th harmonic to the input terminals on the other side of the multiplier MM,. These signals K, through Km are multiplied with the signal X, in the multiplier MM,. As a result, the multiplier MM, produces digital signals K,-X,, K 'X,, K,,,-)(, at the output terminals thereof.

The signal K X, is applied to an adder ADD the signal K X, to an adder ADD the signal K X to an adder ADDm respectively. No other inputs are applied to these adders ADD, through ADDm under the assumed condition. Accordingly, the output of the adder ADD is X X This output lax, of the adder ADD is applied to the other input terminal of the multiplier ML, as a control signal. The wave shape digital signal from the memory Ma is multiplied with this control signal in the multiplier ML The result of the multiplication is provided as the output of the multiplier ML This output contains, for example, eight digits counting from the most significant digit, the remaining digits being discarded. The digital signal from the multiplier ML, represents the wave shape amplitude of the fundamental wave controlled in its level by the control signal. Thus, the fundamental wave output the level of which corresponds to that of the desired tone-color is obtained as a digital signal at the output terminal of the multiplier ML,.

Similarly, a control signal K X is produced as the output of the adder ADD, and the second harmonic output corresponding in its level to the desired tonecolor is produced from the multiplier ML,. The same operation principle applies to the other harmonic outputs.

The foregoing description has been made with regard to the case wherein the musical tone wave shape of the tone-color corresponding to the knob S only is to be obtained. For obtaining a musical tone wave shape composed of a plurality of tone-colors by manipulating a plurality of knobs, digital signals are applied from predetermined ones among the multipliers MM, through MM to the adders ADD through ADDm. The adders ADD, through ADD respectively add the digital signals of live bits and supply sum signals each containing, for example, eight digits counting from the most significant digit to the multipliers ML through MLm as control signals of eight bits. Other operations are the same as described hereinabove with respect to the case wherein only the knob S is operated.

The digital signal outputs from the multipliers ML through MLm are applied to the adder ADD where these signals are added together. The result of the addition including, for example, 12 digits counting from the most significant digit is applied to the digital-to-analog converter DA. Thus, the desired musical tone wave shape composed of the fundamental wave and each harmonic having predetermined relative levels is provided at the output terminal 3.

The spectra memories SM, through SM, store specific wave shapes according to a tone-color to be obtained. If it is desired to change the tone-color, these spectra memories may be detachably connected to the multipliers so that they may be replaced by other ones corresponding to the new tone-co ors.

The portion enclosed by a dotted line in FIG. 4 shows another feature of the apparatus according to this invention. A spectra memory SMx consists of a memory such as a random access memory (RAM) in which information can be written. In order to change the information stored in this memory SMx, a punched card PC containing information corresponding to the levels of the fundamental wave and each harmonic is inserted into a reading device R0 and the output of the reading device RO is applied to the memory SMx. The output of a variable resistor VRx is converted to a digital signal in an analog-to-digital converter Am: and applied to a multiplier MMx. The output of the multiplier MM): is applied to the adders ADD through ADDm and the same operation as described hereinabove is performed to produce the desired musical tone wave shape at the output terminal 3.

1n the foregoing embodiments, the frequency of the clock pulse from the clock pulse generator I was represented as Nf and the musical tone wave shape having the fundamental frequency f, i.e., the wave shape of a musical tone at a specific pitch corresponding to the frequency f is obtained at the output terminal 3. According to the invention, each memory is read at the same reading rate so that the wave shape of a musical tone at a desired pitch can be obtained by merely varying the frequency of the clock pulse from the clock pulse generator 1.

What we claim is: 1. Apparatus for synthesizing electrical wave shapes for conversion into musical tones, comprising a. a plurality of memories for storing in analog representation respective consecutive series of amplitudes of a fundamental sinusordal wave and of selected harmonics thereof; b. a corresponding plurality of read-out means for producing individual voltage signals corresponding to the series of amplitudes stored in each memory;

c. adjustable means for operating said read-out means at the same desired reading rate for each memory;

d. a corresponding plurality of control means for varying as desired the magnitudes of said individual voltage signals;

e. an output terminal for receiving the individual electrical signals to produce a combined output signal having the desired electrical wave shape.

2. Apparatus according to claim 1, in which each memory comprises a voltage source, and a series of resistors connected thereto and adapted to provide individual voltages corresponding to the stored amplitudes, and each read-out means comprises a terminal and individual connections to said resistors, said adjustable means comprising a clock pulse generator connected to a cascade of binary counters corresponding with the number of resistors for successively energising the resistors and producing a continuous series of voltage signals at said terminal.

3. Apparatus according to claim 2, in which each control means comprises a variable amplifier connected to the terminal of the corresponding read-out means of each memory, a selection knob, a variable resistor having a slider interlocked with said knob, an adjustable resistor circuit connected to said slider, and a voltage source for energizing said resistors, a gain control circuit being provided to receive a voltage from said resistors determined by the position of said slider and apply a control voltage to said variable amplifier which thereby produces an individual voltage signal dependent on the operation of the selection knob.

4. Apparatus for synthesizing electrical wave shapes for conversion into musical tones, comprising a. a plurality of wave shape memories in which digital signals are stored corresponding to respective consecutive series of sample amplitudes of a fundamental sinusoidal wave and of selected harmonics thereof;

b. a corresponding plurality of read-out means coupled to the memories for producing individual digital signals out of storage from the memories;

c. adjustable means for operating the respective readout means at the same desired reading rate for each memory;

(1. a corresponding plurality of control means for producing respective digital control signals, each digital control signal corresponding to a respective tone color;

e. a corresponding plurality of multiplier means respectively coupled to corresponding ones of said memories and said control means for multiplying each read-out digital signal with its corresponding digital control signal to produce respective digital product signals;

f. digital adder means for adding said digital product signals from said plurality of multiplier means to produce a digital sum signal; and

g. a digital-to-analog converter means for converting said digital sum signal to an analog output signal having the desired electrical wave shape.

5. Apparatus according to claim 4, wherein said readout means comprises a cascade-connected binary counter, the input of which is connected to a clock pulse generator, the outputs of which are connected in common to the inputs of a plurality of decoders, each of said decoders having a plurality of output lines connected to respective read-out control terminals of one of said memories and providing a read-out signal on one of the output lines corresponding to the count of said binary counters.

6. Apparatus according to claim 4, wherein each of said control means comprises a selection knob, an adjustable resistor having a slider interlocked with said knob, a resistor circuit connected to said slider to produce an analog control signal, a voltage source for energizing said resistor, and an analog to digital converter for converting the analog control signal to the digital control signal.

7. Apparatus according to claim 4, wherein said control means includes means for selectively producing digital amplitude signals respectively representing the amplitudes of the respective tone colors, a plurality of spectra memories in which digital signals are stored representing relative levels of the fundamental wave and the selected harmonics thereof in said desired electrical wave shape, digital multipliers for multiplying the digital signals from the spectra memories with the digital amplitude signals, and digital adders connected to receive the outputs of said multipliers for producing said digital control signals.

8. Apparatus according to claim 7, wherein said means for producing the digital amplitude signals comprise a plurality of tone-color selection knobs, variable resistors each having a slider which is interlocked with one of said knobs, a source of voltage connected across said variable resistors, and analog-to-digital converters for converting the voltages appearing at the sliders of said variable resistors to said digital amplitude signals.

9. Apparatus according to claim 7 in which at least one spectra memory is of a type in which stored information can be changed by writing new information thereinto and which comprises an external input information medium containing information representing the levels of the fundamental wave and of each selected harmonic thereof, and reading means for reading the information contained in said information medium and applying the read information to said at least one memory. 

1. Apparatus for synthesizing electrical wave shapes for conversion into musical tones, comprising a. a plurality of memories for storing in analog representation respective consecutive series of amplitudes of a fundamental sinusordal wave and of selected harmonics thereof; b. a corresponding plurality of read-out means for producing individual voltage signals corresponding to the series of amplitudes stored in each memory; c. adjustable means for operating said read-out means at the same desired reading rate for each memory; d. a corresponding plurality of control means for varying as desired the magnitudes of said individual voltage signals; e. an output terminal for receiving the individual electrical signals to produce a combined output signal having the desired electrical wave shape.
 2. Apparatus according to claim 1, in which each memory comprises a voltage source, and a series of resistors connected thereto and adapted to provide individual voltages corresponding to the stored amplitudes, and each read-out means comprises a terminal and individual connections to said resistors, said adjustable means comprising a clock pulse generator connected to a cascade of binary counters corresponding with the number of resistors for successively energising the resistors and producing a continuous series of voltage signals at said terminal.
 3. Apparatus according to claim 2, in which each control means comprises a variable amplifier connected to the terminal of the corresponding read-out means of each memory, a selection knob, a variable resistor having a slider interlocked with said knob, an adjustable resistor circuit connected to said slider, and a voltage source for energizing said resistors, a gain control circuit being pRovided to receive a voltage from said resistors determined by the position of said slider and apply a control voltage to said variable amplifier which thereby produces an individual voltage signal dependent on the operation of the selection knob.
 4. Apparatus for synthesizing electrical wave shapes for conversion into musical tones, comprising a. a plurality of wave shape memories in which digital signals are stored corresponding to respective consecutive series of sample amplitudes of a fundamental sinusoidal wave and of selected harmonics thereof; b. a corresponding plurality of read-out means coupled to the memories for producing individual digital signals out of storage from the memories; c. adjustable means for operating the respective read-out means at the same desired reading rate for each memory; d. a corresponding plurality of control means for producing respective digital control signals, each digital control signal corresponding to a respective tone color; e. a corresponding plurality of multiplier means respectively coupled to corresponding ones of said memories and said control means for multiplying each read-out digital signal with its corresponding digital control signal to produce respective digital product signals; f. digital adder means for adding said digital product signals from said plurality of multiplier means to produce a digital sum signal; and g. a digital-to-analog converter means for converting said digital sum signal to an analog output signal having the desired electrical wave shape.
 5. Apparatus according to claim 4, wherein said read-out means comprises a cascade-connected binary counter, the input of which is connected to a clock pulse generator, the outputs of which are connected in common to the inputs of a plurality of decoders, each of said decoders having a plurality of output lines connected to respective read-out control terminals of one of said memories and providing a read-out signal on one of the output lines corresponding to the count of said binary counters.
 6. Apparatus according to claim 4, wherein each of said control means comprises a selection knob, an adjustable resistor having a slider interlocked with said knob, a resistor circuit connected to said slider to produce an analog control signal, a voltage source for energizing said resistor, and an analog to digital converter for converting the analog control signal to the digital control signal.
 7. Apparatus according to claim 4, wherein said control means includes means for selectively producing digital amplitude signals respectively representing the amplitudes of the respective tone colors, a plurality of spectra memories in which digital signals are stored representing relative levels of the fundamental wave and the selected harmonics thereof in said desired electrical wave shape, digital multipliers for multiplying the digital signals from the spectra memories with the digital amplitude signals, and digital adders connected to receive the outputs of said multipliers for producing said digital control signals.
 8. Apparatus according to claim 7, wherein said means for producing the digital amplitude signals comprise a plurality of tone-color selection knobs, variable resistors each having a slider which is interlocked with one of said knobs, a source of voltage connected across said variable resistors, and analog-to-digital converters for converting the voltages appearing at the sliders of said variable resistors to said digital amplitude signals.
 9. Apparatus according to claim 7 in which at least one spectra memory is of a type in which stored information can be changed by writing new information thereinto and which comprises an external input information medium containing information representing the levels of the fundamental wave and of each selected harmonic thereof, and reading means for reading the information contained in said information medium and applying the read information to said at least one memory. 